The present invention relates to a method of composing a VPN (Virtual Private Network) on the Internet and an interwork router used to connect Internet service providers to each other.
Various applications such as E-mail and WWW (World Wide Web) programs can be used on any Internet Protocol (IP) networks. In addition, such IP networks can be composed at lower costs than the conventional switching networks that use are associated with telephones. This is why the Internet has rapidly come into wide use in recent years. Under such circumstances, intracompany networks (intranets) composed on the IP level are now indispensable for facilitating the activities of those companies.
Companies are often distributed unevenly in local areas. In such a situation, therefore, there will appear a demand that the intranets in those local areas should be connected into one network as a logical consequence. In such a case, there are the following two methods possible for connecting those intranets to each other in local areas.
Firstly, private lines are used for connecting those intranets in local areas. In this case, each of those intranets can be isolated from external networks for ensuring security.
Secondly, the IPsec (IP security protocol) technique is used to provide each terminal with a function for identifying packets of its own company""s network, so that those packets are transferred on the Internet as IP packets using global addresses. This identifying function, when combined with an encoding technique, can make up a Virtual Private Network (VPN) so as to be protected from the attacks of malicious users.
If such private lines are used; however, some problems arise; for example, the network cost is increased, and furthermore, the VPN realized by the IPsec method cannot be protected from the attacks and invasions of malicious users who can crack the codes. In addition, the encoding processing becomes a bottleneck of increasing the speeds for fast networks and terminal costs are increased.
Along with the rapid spread of the Internet, as well as the cost reduction of using the Internet, there have appeared strong demands for forming virtual private networks on the Internet using the functions of lower layers than the IP layer provided by networks, while suppressing the cost and isolating each of those virtual private networks from external networks so as to assure the security and quality thereof.
In order to meet such demands, the following VPN is proposed. A packet is encapsulated at the inlet of the object network of an Internet Service Provider (ISP) that provides the VPN. On the ISP network, each packet is transferred according to the capsule header, then the capsule header is removed at the outlet of the network. According to this VPN composing method, since a packet is encapsulated peculiarly to the VPN, the VPN is isolated from external networks, thereby assuring the security of the VPN. More concretely, for such an encapsulation protocol various methods are available, such as IP encapsulation, MPOA (Multi Protocol over ATM), MPLS (Multi Protocol Layer Switching), etc. Since February of 1999, those methods have been under examination in such standardization groups as ITU-T SG13 (International Telecommunications Union-Telecommunications Standardization Section, Study Group 13), IETF (Internet Engineering Task Force), etc. In addition, ITU-T SG13 is also examining the Core Protocol of the Global Multi-media Network Connection Less (GMN-CL) for transferring packets encapsulated according to E.164 addresses in the object network.
xe2x80x9cAccess Network Systems and Edge Nodes Systems for the Next-Generation Computer Networkxe2x80x9d, pp.425-434, NTT RandD vol.47 No.4, 1998 (issued on Apr. 10, 1998) has also proposed a method for composing an edge node in an accessing system used to interwork between each of a plurality of user networks and the core network in the GMN-CL.
In recent years, the areas of activities in companies have expanded more and more widely. For example, many Japanese companies have offices at overseas, including the United States of America and European countries. Under such circumstances, it would be natural for those companies to consider it important to connect the intranets composed in their offices to each other via a VPN.
On the other hand, since each ISP generally provides the services only in a specific area, the VPN must be composed over a plurality of ISPs in order to connect the networks (intranets) in those areas through the VPN.
And, if a plurality of ISPs are connected to each other in such a way, an interwork gateway (interwork router) needs to be formed for such connection. In this interwork router, the interwork is realized so as to transfer each of the packets from one of the ISP networks to the other according to the IP header. In addition, a system referred to as an IX (Internet Exchange) is used for connecting both networks to each other so as to realize the interwork among a plurality of networks as described in xe2x80x9cCommercial IXxe2x80x9d, pp.146-155, Nikkei Communications 1997.12.15. And, this IX may also be used to transfer IP packets among those networks. Such an IX includes some methods that use a xe2x80x9clayer 3 forwardingxe2x80x9d function for identifying and transferring each of the IP packets, as well as a xe2x80x9clayer 2 forwardingxe2x80x9d function for transferring each of the IP packets by identifying the header in the lower layer in the ATM (Asynchronous Transfer Mode) communication system, etc.
The present inventors have examined the problems which arise when a VPN is composed over a plurality of ISP networks. At first, packets are encapsulated in order to compose a VPN for the network of each Internet Service Provider. Generally, the encapsulation protocol of each network differs from other networks. In this case, the IP header information of each IP packet is retrieved by the interwork router, thereby determining the route to the destination. In this case, the retrieving must also include a check to determine whether or not the packet is to be transferred to another network. The IP header information is common for both of the networks.
However, the interwork router terminates the protocol of each layer lower than the IP layer at the interface. Therefore, the capsule header given in the previous network so as to compose the VPN is removed in the process of retrieving the IP address, so that information as to the next leg of the route can be determined. After that, a new capsule header must be generated and added to the packet so as to compose the VPN in the next network. Consequently, packets in the VPN are mixed with packets in other networks in the interwork router. And, this might cause a problem that malicious users are able to change the headers to those packets and invade the VPN through the interwork router.
Some companies do not use global addresses, but use private addresses for composing their VPNs. In such a case, once the interwork router removes the capsule header of a packet, the receiving ISP cannot distinguish the packet from others if the packet has the same address as those of other packets. This is because each of a plurality of VPNs use internal addresses uniquely. Consequently, the receiving ISP receiving cannot determine the destination of the packet. If a VPN is composed over a plurality of ISPs on the Internet, therefore, the problem as described above be solved by all means.
In addition, the types of services are not the same among ISPs. As for the communication quality, for example, assume that one ISP uses an ATM VC (Virtual Channel) for forming a communication path, thereby assuring the quality of each VPN and the other ISP uses Diffserv (Differentiated Services) to assure the quality of the communication. If the VPNs composed for both networks are to be connected to each other in such a case, it will be difficult to provide the communication quality on an end-to-end level.
As described above, it is difficult to compose a VPN over a plurality of ISPs on the Internet for practical use.
Under such circumstances, therefore, it is an object of the present invention to solve the above problems and provide a method of composing a VPN over a plurality of ISPs and provide an interwork router for connecting those ISPs to each other in such a VPN.
In order to solve the above problems, the interwork router of the present invention is provided with functions for determining the route to output packets and for generating a capsule header for each of those packets to be used in the next ISP network (in output side) from the information set both in the capsule header, which is a VPN identifier, and in the IP header of the packet. Hereunder, a more detailed description will be made of an example of how to connect a plurality of ISPs to each other. Each of those ISPs is used to operate an MPLS network that uses an ATM as a lower layer. More concretely, header information is added to each packet to be transferred to the next network. Such header information is generated when header information such as VPI, VCI, etc. (capsule headers) of the ATM are used to identify the VPS, as well as to determine the next route and identify the VPN in the next network, which header information is generated with necessary data retrieved according to an IP address as a key. And, the header information is generated and transferred together with the packet to the next network.
A VPN interwork can thus be realized, thereby enabling the VPN to be composed on the Internet in areas covering a plurality of ISPs.
The value of the field that indicates the QoS in the capsule header on the input side is mapped on the value of the field that indicates the QoS in the capsule header for the output side. Consequently, quality information of both networks composing a VPN can be transferred as is.